Correction of astigmatism using rotationally symmetric contact lenses

Abstract

A rotationally symmetric contact lens has a reservoir formed centrally on the posterior surface thereof to provide an additional optical power of up to 1.51 diopters. The reservoir may be spherically or aspherically shaped.

What is claimed is: 
     
       1. A rotationally symmetric contact lens comprising: a rotationally symmetric substantially convex anterior surface;   a rotationally symmetric substantially concave posterior surface; and   a reservoir having a substantially concave surface and being disposed centrally in the posterior surface, the diameter of the reservoir being substantially less than the diameter of the posterior surface of the lens, the reservoir being shaped to provide additional optical power centrally, and shaped to provide optical correction for an astigmatic condition, the shape of the reservoir is selected to provided an optical power of less then 1.51 diopters,   wherein the substantially concave posterior surface has an outer peripheral rim engageable with the eve which is substantially smooth and non-channeled.   
     
     
       2. A rotationally symmetric contact lens according to claim 1, wherein the reservoir is spherical in shape. 
     
     
       3. A rotationally symmetric contact lens according to claim 1, wherein the reservoir is aspherical in shape. 
     
     
       4. A rotationally symmetric contact lens according to claim 1, wherein the anterior surface is aspherical and the posterior surface external to the reservoir is aspherical. 
     
     
       5. A rotationally symmetric contact lens according to claim 1, wherein the anterior surface is spherical and the posterior surface external to the reservoir is spherical. 
     
     
       6. A rotationally symmetric contact lens according to claim 1, wherein the anterior surface is spherical and the posterior surface external to the reservoir is aspherical. 
     
     
       7. A rotationally symmetric contact lens according to claim 1, wherein the lens is made of a soft, hydrophillic polymeric material. 
     
     
       8. A rotationally symmetric contact lens according to claim 1, wherein the lens is made of a hard hydrophobic material. 
     
     
       9. A rotationally symmetric contact lens according to claim 1, wherein the anterior surface is aspherical and the posterior surface external to the reservoir is spherical. 
     
     
       10. A method of correcting astigmatism comprising the steps of: forming rotationally symmetric anterior and posterior surfaces of a corneal contact lens to provide fitting and optical power;   forming a reservoir in the posterior surface of the contact lens, said reservoir being shaped to provide an additional optical power centrally and shaped to provide optical correction for an astigmatic condition, the shape of the reservoir is selected to provide an optical power of less than 1.51 diopters;   wherein the diameter of the reservoir is substantially less than the diameter of the posterior surface of the lens; and   wherein the substantially concave posterior surface has an outer peripheral rim engageable with the eve which is substantially smooth and non-channeled.   
     
     
       11. A method according to claim 10, wherein the reservoir has a spherical shape. 
     
     
       12. A method according to claim 10, wherein the reservoir has an aspherical shape. 
     
     
       13. A method according to claim 10, wherein the anterior surface is spherical and the posterior surface external to the reservoir is spherical. 
     
     
       14. A method according to claim 10, wherein the anterior surface is spherically shaped and the posterior surface external to the reservoir is aspherically shaped. 
     
     
       15. A method according to claim 10, wherein the anterior surface is aspherically shaped and the posterior surface external to the reservoir is spherically shaped.